Warner Bros. Pictures' Harry Potter and the Half-Blood Prince earned an estimated $22.2 million for its 3,003 midnight screenings, beating the $18.5 million midnight runs by the studio's own The Dark Knight and the $16.9 million earned by Star Wars: Episode III Revenge of the Sith.

The sixth installment continues its first day of release in 4,275 domestic locations and will expand to 4,350 theaters on Friday.

Last month, Michael Bay's Transformers: Revenge of the Fallen grossed $16 million in midnight runs, also on a Wednesday.

"Half-Blood Prince" opened in the same Wednesday slot that Harry Potter and the Order of the Phoenix did in 2007. "Order of the Phoenix" grossed $12 million in midnight runs on its way to a $139.7 million five-day debut.